1. Field of the Invention
The present invention relates to a method of forming mask pattern data to be used for high-precisely transferring a micropattern in projection exposure using double-pole illumination or quadrupole illumination, a photomask manufactured by using the mask pattern data forming method, and a method of manufacturing a semiconductor device using the photomask.
2. Description of the Related Art
In recent years, a resolution close to a theoretical limitation determined on the basis of a wavelength of light has been required accompanying the miniaturization of a device pattern. Various phase shift masks have been proposed as a photomask toward the request. Further, as an exposure apparatus, a grazing-incidence illuminating system exposure apparatus by which a light incident into a photomask is illuminated so as to be inclined from the optical axis by an angle corresponding to a numerical aperture of a projection exposure apparatus has been proposed. Moreover, an exposure system in which a phase shift mask and a grazing-incidence illuminating system are combined has been under review.
In particular, in a memory device, extreme miniaturization has been required for patterns arranged in a specific direction in a cell array (for example, in an X direction or a Y direction). In order to realize the request, it has attracted attention that a double-pole illumination method or a quadrupole illumination method is used in a grazing-incidence illuminating system (for example, refer to Jpn. Pat. Appln. KOKAI Publication Nos. 4-101148 and 4-180612). A high resolution and an exposure margin are improved by using double-pole illumination and quadrupole illumination for patterns with a minute pitch of a cell array.
However, in double-pole illumination and quadrupole illumination, there is the problem that the resolution and the depth of focus (DOF) with respect to patterns with a pitch which is greater to some extent than those of patterns randomly arrayed in a device pattern and of patterns of a cell array. Namely, although an exposure margin with respect to a cell array is improved by using double-pole illumination and quadrupole illumination, there is the problem that an exposure margin is low with respect to a complex layout pattern. As a complex layout pattern, there is representatively an interconnecting wiring pattern for connecting a cell array portion and a core region or a peripheral region which has a relatively loose pitch, but includes a complex pattern layout.
In this way, conventionally, when double-pole illumination or quadrupole illumination is used, a degradation in an exposure margin with respect to an interconnecting wiring pattern from a memory cell array to a peripheral region, and in particular, with respect to an interconnecting wiring pattern from a minute pitch region of a cell array to an eased pitch region at the peripheral portion has become a big problem.